Vacuum indicating buttons on closures are used extensively for the food industry because they are an effective quick-detection means that lets one know some very important conditions about the container. For example: Is the container sealed? - button is in "down" position; has the container been opened, or tampered? - button is in "up" position; has the seal been broken because of other causes, such as: severe handling, slow leakage or cracked glass at the seal area that could result in product spoilage. It is also very reasurring to hear the button "pop" as the closure is twisted off of the container. In addition, the button is an invaluable quality control means at the product filling operation. With automatic type detection equipment it lets the packer know, instantly, whether to accept the sealed container (button down), or reject it (button up), because a seal was not attained. Moreover, the vacuum indicating button on a closure has greatly increased in usage as a tamper indicating means in recent years.
Further, in more recent years, the position of the button and the "pop" noise made thereby when a container is opened, have not been the only usage. More recently, it has been proposed to utilize the movement of the button or other panel area of a closure to provide for a permanent indication of container opening. For example, it has been proposed to provide a frangible or brittle type coating that can be irreversibly fractured by the movement of a panel portion (button) that may, for example, provide a color change to indicate that a container is either presently opened or has been previously opened and reclosed.